In our framework, as in [1]}, we are given a finite input set \(P\)  of items that are called points, a (usually infinite) set \(Q\)  of items that are called queries, and a cost function \(f\)  that maps each pair of a point in \(P\)  and a query in \(Q\)  to a non-negative number \(f(p,q)\) . The cost of the set \(P\)  to this query is the sum over all the costs,
\(\bar{f}(P,q):=\sum _{p\in P}f(p,q).\) 
